Lemonia Ragia, "Ein Modell für die Qualität räumlicher Daten zur Bewertung der photogrammetrischen Gebäudeerfassung". Thesis at: Institute of Photogrammetry, University of Bonn. 2001.

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Summary
Geoinformation Systems have gained in importance over years. These systems deal with spatial relationships and require data of high quality. This work contributes to the automatic quality control of available data on spatial objects. The data may be provided from different sources. The spatial objects can be observed in planimetry and the outlines are represented by polygons. The uncertainty of their boundaries is taken into consideration. The objects are composed of many parts. A quality model is defined to access the data quality. It is based on quality descriptions parameters. Input to the evaluation of the parameters of the quality model are different descriptions of a scene. One description is used as a reference and the other for a quality control. The descriptions are analysed geometrically and topologically. The topological analysis is based on the neighbourhood structure and the geometric analysis of the footprint structure. The existence of an object is asserted by the quality parameter "success". The specifications of the data are also modelled in the quality model. An identification and detection of topological and geometrical inconsistencies is provided. The metaquality is also modelled. A representation of complex objects with graphs has several advantages. The object parts neighbourhood graph represents the internal structure the descriptions. The object part correspondence graph represents the relationships of the object parts and the object correspondence graph represents the relationships of the objects. A zone skeleton and a distance function is used for describing the geometrical differences. The proposed process is verified on real examples. It was applied successfully in 10 test areas of 10 cities with different building characteristics. A quality protocol is generated automatically. The traffic light principle is used for the evaluation of the quality parameter groups, the quality parameters and the overall performances: Rather than binary decisions three categories are defined: accepted (green), rejected (red) and subject for review (yellow). Thresholds and weights are produced in order to access the quality differences.
Zusammenfassung
Geoinformationssysteme haben in den letzten Jahren zunehmende Bedeutung erlangt. Diese Systeme bearbeiten räumliche Zusammenhänge und erfordern gut kontrollierte Daten. Diese Arbeit liefert einen Beitrag zur automatischen Qualitätskontrolle von räumlichen Objekten. Die Objekte können mit beliebigen Verfahren erfaßt worden sein. Die Objekte werden zweidimensional betrachtet, wobei der Umriß durch eine Polygonlinie dargestellt wird. Die Unsicherheit des Randes der Objekte wird berücksichtigt. Die Objekte können aus mehreren zusammenhängenden Objektteilen bestehen. Um die Qualität beurteilen zu können, wird ein Qualitätsmodell definiert. Es basiert auf der Modellierung von Qualitätsparametern. Eingangsdaten in das Verfahren zur Berechnung der Parameter des Qualitätsmodells sind zwei unterschiedliche Beschreibungen einer Szene. Eine Beschreibung dient als Referenz und die andere ist die zu kontrollierende. Die Beschreibungen werden topologisch und geometrisch analysiert. Die Topologie basiert auf der Nachbarschaftsstruktur, und die Geometrie auf der Umrißstruktur und Lage. Die Existenz der Objekte wird unter der Qualitätsparametergruppe "Erfolg" analysiert. In dem Qualitätsmodell wird die Spezifikation der Daten mitmodelliert. Eine automatische Identifikation und Detektion der topologischen, geometrischen Inkonsistenzen wird erzeugt. Ebenfalls wird die Metaqualität modelliert. Für die Analyse hat sich die Repräsentation der komplexen Objekte durch Graphen als vorteilhaft erwiesen. Der Objektteil-Nachbarschaftsgraph stellt die innere Struktur beider Beschreibungen, der Objektkorrespondenzgraph die Zuordnung der Objekte und der Objektteil-Korrespondenzgraph die Zuordnung der Objektteile dar. Ein Zonenskelett und eine Distanzfunktion werden für die Charakterisierung der geometrischen Unterschiede benutzt. Das Verfahren wurde an realen Beispielen überprüft. Es wurde auf insgesamt 10 Testgebiete aus 10 Städten mit stark unterschiedlicher Bebauung erfolgreich angewandt. Ein Qualitätsprotokoll wird automatisch erzeugt. Für die Bewertung der Qualitätsparametergruppen, der Qualitätsparameter, sowie der Gesamtbeurteilung wurde das Ampel-Prinzip benutzt: Hier werden statt binären Entscheidungen die drei Kategorien akzeptiert (grün), abzulehnend (rot) und zu untersuchend (gelb) benutzt. Es werden Schwellwerte und Gewichte erarbeitet, um eine bessere Beurteilung der Qualitätsunterschiede zu ermöglichen.

@phdthesis{Ragia2001Ein,
  author = {Ragia, Lemonia},
  title = {Ein Modell f\"ur die Qualit\"at r\"aumlicher Daten zur Bewertung der photogrammetrischen Geb\"audeerfassung},
  school = {Institute of Photogrammetry, University of Bonn},
  year = {2001},
  note = {GMD Series No.14}
}

Lemonia Ragia, "A Quality Model for Spatial Objects", In Proceedings of the 19th ISPRS Congress. Amsterdam, pp. 855-862, 4C. 2000.

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This paper presents a concept for analysing the quality of 2 1/2 - D spatial objects. The developed method is based on the evaluation of specific quality parameters. These parameters are determined by a topological and geometrical analysis. The quality parameters are classified into three categories: green=accepted, yellow=uncertain, red=rejected, depending on the specifications. We give confidence regions for all quality parameters, especially for completeness, false alarm rate and detection rate. The feasibility of the method is shown by using real examples taking into account the technical specifications.

@inproceedings{Ragia2000Quality,
  author = {Ragia, Lemonia},
  title = {A Quality Model for Spatial Objects},
  booktitle = {Proceedings of the 19th ISPRS Congress},
  year = {2000},
  pages = {855--862, 4C}
}

Lemonia Ragia and Wolfgang Förstner, "Automatically Assessing the Geometric and Structural Quality of Building Ground Plans", In Proceedings of ISPRS Working Group II/6, International Workshop on 3D Geospatial Data. Paris, France 1999.

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The paper develops an approach for assessing the quality of ground plans of buildings. Quality is measured not only by geometrical but also by structural differences between an acquired data set and a reference data set. New hybrid techniques for automatically determining quality measures are developed, and shown to be applicable to real data. The uncertainty of the given data is taken into account. Automating quality assessment increases efficiency in checking data, allowing complete checks instead of sampling, moreover it makes quality checks objective. The developped techniques are applicable to sets of 2D regions of any type and internal structure. We also demonstrate the necessity to use the quality of the quality parameters when checking the fullfillment of quality specifications.

@inproceedings{Ragia1999Automatically,
  author = {Ragia, Lemonia and F\"orstner, Wolfgang},
  title = {Automatically Assessing the Geometric and Structural Quality of Building Ground Plans},
  booktitle = {Proceedings of ISPRS Working Group II/6, International Workshop on 3D Geospatial Data},
  year = {1999}
}

Eberhard Gülch and Hardo Müller and Thomas Läbe and Lemonia Ragia, "On the performance of semi-automatic building extraction", In Proceedings of ISPRS Commission III Symposium. Columbus, Ohio 1998.

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A Semi-Automatic Building Extraction system using two or more digitized overlapping aerial images has been enhanced by increased automation for the measurement of saddle-back-roof buildings, hip-roof buildings and boxes. All newly developed modules have been incorporated in the object oriented design of the system. The new methods consist of a ground-point and roof-top matching tool and a robust determination of shape parameters, like e.g. gutter length and width. The current performance of building extraction is quantitatively and qualitatively evaluated. We examine the increased efficiency using the automated tools, the success rate of individual modules and the overall success rate using a combination of methods. A methodology for quantitative comparison is tested on footprints of buildings from classical stereo measurements and from semi-automatic measurements. A qualitative comparison in 3D of multiple measurements of complete buildings is performed on three different datasets.

@inproceedings{Gulch1998performance,
  author = {G\"ulch, Eberhard and M\"uller, Hardo and L\"abe, Thomas and Ragia, Lemonia},
  title = {On the performance of semi-automatic building extraction},
  booktitle = {Proceedings of ISPRS Commission III Symposium},
  year = {1998}
}

Stephan Winter and Lemonia Ragia, "Contributions to a Quality Description of Areal Objects in Spatial Data Sets", In Proceedings of ISPRS Commission IV Symposium. Stuttgart, Germany 1998.

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In this paper we present a quality evaluation of two-dimensional building acquisition. We propose methods for identification and quantification of differences between independently acquired regions, and we present a systematic classification of those differences. Differences between acquired sets Rj = rij of regions rij depend on the context of observation, on the technique of observation, and so on. We distinguish topological and em geometrical differences. Topological differences refer to the interior structure of a set of regions as well as to the structure of the boundary of a single region. Geometrical differences refer to the location of the boundary of a single region or of a set of regions, independent of their representation and of the structure of the boundaries. Identification of differences requires a matching of two data sets R1 and R2 which is done here by weighted topological relationships. For the identification of topological differences between two sets R1 and R2 of regions we use the two region adjacency graphs. For an identification of geometrical differences we use the zone skeleton between two matched subsets rp1 and rq2 of the given sets. The zone skeleton is labeled with the local distances of the corresponding boundaries of the subsets; especially we investigate its density function. An example, based on two real data sets of acquired ground plans of buildings, shows the feasibility of the approach.

@inproceedings{Winter1998Contributions,
  author = {Winter, Stephan and Ragia, Lemonia},
  title = {Contributions to a Quality Description of Areal Objects in Spatial Data Sets},
  booktitle = {Proceedings of ISPRS Commission IV Symposium},
  year = {1998}
}